Railway signaling apparatus



P 1940- B. E. OHAGAN 2,215,821

RAILWAY S IGNALING APPARATUS Filed June 24, 1939 3 Sheets-Sheet 2 8 Zl/0 11 q j DIEZa; I

lNV TOR Bern ar Oflzzyan.

HIS ATTORNEY Sept. 24, 1940.

B. E. O'HAGAN RAILWAY SIGNALING APPARATUS Filed June 24, 1959 5Sheets-Sheet 3 INV NTOR Berna/r" .OHayan.

H 15 ATTORNEY Patented Sept. 24, 1940 UNITED STATES PATENT OFFICE2,215,821 RAILWAY SIGNALING APPARATUS Application June 24, 1939, SerialNo. 280,997

24 Claims. (01. 246-34) My invention relates to railway signalingapparatus, and has particular reference to apparatus of the typeemployed in railway signaling systems in which coded trackway energy isutilized to control either or both wayside signals and train carried cabsignals.

It has hitherto been proposed to employ relays of the saturation type ascode following relays in connection with signaling systems utilizingcoded trackway energy. I have found that when saturation type codefollowing relays are so employed, the energy reproduced in such relaysin response to the coded trackway energy may be distorted, that is, thelength of the code impulse induced in the saturation relays may beprolonged, and also there may be a residual output of the relays duringthe off or no energy period of the trackway code. Accordingly, an objectof my invention is the provision of novel and improved means foremploying code following relays of the saturation type in coded trackcircuit signaling systems, whereby more eflicient and improved operationof such relays is effected by the coded trackway energy.

A further object is the provision of improved cut-section facilities forcascading trackway en-,

ergy around a cut in a track section. Thesefacilities are an improvementupon the apparatus shown in a copending application, Serial No. 280,371,filed on June 23, 1939, by Claude M. Hines, and certain featuresdisclosed in the present case are broadly claimed in the said copendingapplication.

Another object is the provision of novel and improved forms of relays ofthe saturation type, especially adaptable for use in systems of theabove class.

A further object is to prevent distortion in the coded output of suchrelays when used as code following relays.

An additional object is to prevent such distortion by preventing theprolongation of the code impulses induced in such relays.

Another object is to prevent distortion of the code output of suchrelays by decreasing the residual output of such relays.

Other objects and advantages of my invention will appear as thedescription proceeds.

I shall describe three forms of apparatus embodying my invention, andshall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a diagrammatic view showing apreferred form of ap-' paratus embodying my'invention. Figs. 2 and 3 arediagrammatic views showing modified forms of the apparatus shown in Fig.1, each also embodyl'ng my invention.

Similar reference characters refer to similar parts in each of theseveral views.

Referring first to Fig. 1, the reference characters I and la designatethe track rails'of a stretch of railway track over which trafiicnormally moves in the directionindicated by an arrow in the drawing, andwhich direction I shall assume to be the westbound direction. The railsI and I a are divided by means of the usual insulated rail joints 2 intoa plurality of successive adjoining track sections, of which only onesection 34, is shown complete in the drawings. Section 3--4 also isfurther divided into a plurality of subsections, formed by interposinginsulated joints 2 in the rails of section 3-4 at socalled cut-sectionlocations. As shown, the rails I and la of Fig. 1 are provided withinsulated joints 2 at cut-section location 3a, with the result thatsection 3-4 is divided into an advance subsection 3-3a and a rearsubsection 3a4.

Each track section is provided with a signal, designated by thereference character S with a distinguishing sufiix, located adjacent theentrance end of the section for governing traflic operating thereover.Signals S may take any one of many suitable forms but in the form hereinshown are three-indication signals of the color light type, and eachsignal comprises a red lamp R, a yellow lamp Y and a green lamp G, whichlamps when illuminated indicate stop, caution and proceed, respectively.

Each section is further provided with means, located at the exit end ofthe section, for supplying to the rails of the associated section codedtrackway energy, the code frequency or rate of which is controlled bytrafiic conditions in advance. These means are herein shown in the usualform and comp-rise a track transformer, designated by the referencecharacter TI with a distinguishing suffix, the secondary of which isconstantly connected with the rails of the asso- 5 ciated section inseries with the usual current limiting impedance 5. The primary oftransformer TT is connected with the terminals BX and CK of a suitablesource of alternating current (not shown in the drawings) preferably ofa frequency of 100 cycles per second, over one contact I80 or overanother contact 15 of a coding device, designated by the referencecharacter CT plus a distinguishing suflix, according as a with adistinguishing suffix, which is associated with the section next inadvance is closed, only the coding device DT4 and the relay H4 which areassociated with section 3-4 being shown in the drawings. Coding deviceGT6 is constantly supplied with current from a suitable source ofcurrent, the terminals of which are indicated by the referencecharacters BX and GK, and this device constantly opens and closes itscontact I80 at the rate of 180 times per minute, and also opens andcloses its contact I5 at the rate of 75 times per minute. It is readilyapparent, therefore, that when the relay H of a section is picked up sothat its front contact 6-50, is closed, the rails of the section next inthe rear will be supplied with alternating trackway energy which isperiodically interrupted or coded at the rate of 180 times per minute,but that, when the relay H of a section is released so that its backcontact 68b is closed, the rails of the section next in the rear thenwill be supplied with alternating trackway energy which is periodicallyinterrupted or coded at the rate of '75 times per minute. The 180 codeis used to provide a proceed indication and the 75 code is used toprovide a caution indication for the signal of the associated section,in a manner which will be made clear as the description proceeds. Eachrelay H is controlled by traffic conditions in the associated section ina manner which also Will be made clear as the description proceeds.

Each section is provided at its entrance end with a code following trackrelay of what I shall term a front contact relay of the saturation type,designated by the reference character DR with a distinguishing sufiix. Asimilar relay is located also at the cut-section location of eachsection, only the relays DRI and DRIa located respectively at the signallocation 4 and at the cut-section location 3a of section 3-4 being shownin the drawings. The relays DR are substantially similar in constructionso that the following description of relay DRIa will suffice as well todescribe relay DRI.

Relay DRIa, in the form herein shown, comprises a magnetizable core Iprovided with four parallel legs 8, 9, I I] and II connected together ateach end to form an integral core structure. One of the inner legs I isprovided with a pri mary or local input winding I3 constantly connectedwith a source of periodically varying current (preferably beingconnected with a source of alternating current which is indicated in thedrawings by the terminals BX and CK) for setting up a flux in the coreI. The primary flux thus set up in core I normally divides between twomagnetic circuits, one of which I shall term a main circuit, and theother of which I shall term a leakage circuit. The main magnetic circuitof core I comprises the common leg Ill and the adjacent outer leg II,upon which latter leg is mounted a secondary or output winding I4.

The other or leakage magnetic circuit comprises the common leg Ill and,in parallel the legs 8 and 9, upon which legs is disposed a saturationwinding I5, which comprises two coils Ia and I5?) disposed respectivelyon legs 8 and 9, the coils being connected in series in such manner thatthe resultant electromotive force normally induced in winding I5 as aresult of the primary flux created by winding I3 is substantially zero.

, This arrangement of coils I511 and I5?) also is such that when windingI5 is supplied with unidirectional current in a manner to be made clearpresently, the coils act cumulatively to circulate a flux through alocal magnetic circuit formed by the parallel legs 8 and 9 and theadjoining top and bottom portions of the core forming a part of theleakage magnetic circuit of the relay, thereby varying the reluctance ofsuch leakage circuit. The terminals of winding I5 are connected acrossthe output terminals of a rectifier RI, the connection of winding I5with the lower output terminal of rectifier RI including in seriestherewith a resistor XI, which resistor in turn is connected across theoutput terminals of a biasing rectifier R2. The arrangement ofrectifiers RI and R2 in the above circuit is such that the electromotiveforce of rectifier R2 opposes the electromotive force of rectifier RI.The input terminals of rectifier R2 are connected with a suitable sourceof alternating current, which, as here shown, may be a transformer TIhaving its primary winding connected with a source of alternatingcurrent, but if desired, rectifier R2 may be connected to a secondarywinding mounted on leg ID of the core I in inductive relationship withlocal input winding I3.

The saturation winding I5 of relay DRIa is supplied with energy from thetrack rails of subsection 33a through the medium of a relay transformerRTS, which transformer has its primary winding connected across therails of subsection 3-3a, and has its secondary winding connected to theinput terminals of rectifier RI, so that the coded alternating trackwayenergy received from the rails of subsection 3-3a is rectified into andis supplied to winding I5 as impulses of unidirectional current.

The output winding I4 of relay DRIa is connected across the track railsI and Ia of subsection 3a,-4, for a purpose to be made clear presently.

With relay DRIa constructed and arranged in the foregoing manner, it canbe seen that winding I3 is constantly supplied with periodically varyingcurrent so that the primary flux created thereby links both magneticcircuits of its core I. It is apparent, therefore, that during theinterval that the primary flux links both circuits, a voltage of a givenvalue will be induced by such flux in output winding I4. When, however,control winding I5 is supplied with current (as for example during theon period of the code) so that the flux created thereby varies thereluctance of the leakage circuit (the winding I5 being preferably soproportioned as to magnetically saturate the leakage circuit),substantially all the primary flux then will circulate through leg IIwith the result that a greatly increased voltage will be induced inwinding I4 at this time. During the off period of the code, thereluctance of the leakage circuit again will drop and the primary fluxagain divide between the two circuits so that the lower, or given,voltage will be induced in winding I4. It is readily apparent from theforegoing that a relatively high voltage is or is not induced in windingl4 according as winding I5 is or is not supplied with current, and thatthis relatively high voltage will be induced in the winding I4 in stepwith the impulses of current supplied from the rails of the section towinding I5, by virtue of the action of such current impulses in varyingthe reluctance of the leakage magnetic circuit and thereby varying theflux circulating in the main magnetic circuit of the relay. It follows,therefore, that with winding I4 connected across the rails of the rearsubsection 3a4, such rails will be supplied with alternating trackwayenergy of relatively high voltage in step with the code current impulsessupplied to the rails of the advance subsection 3-3a, whereby the codedtrackway energy of subsection 3-3a is cascaded around the cut-sectionlocation 3a by virtue of relay DRIa reproducing the energy in kind andsupplying the reproduced energy to subsection 3a--4.

The resistcr'XI and the biasing rectifier R2 are incorporated into relayDRIa to prevent distortion of the coded energy induced in the secondarywinding of the relay by applying to the control winding I of the relayan electromotive force which opposes the coded electromotive forcepresent at times in that winding. As was pointed out heretofore, controlwinding I5 of relay DRIa is supplied by rectifier RI with coded impulsesof rectified current having a polarity indicated in the drawings, and asa result of the supply of such impulses, the reluctance of the leakagecircuit of the relay core is varied to thereby vary the magneticcoupling of the primary and secondary windings of the relay wherebyimpulses of relatively high voltage are induced in the secondary windingI4 of the relay. But for the provision of resistor XI and rectifier R2,the relatively high voltage impulses induced in secondary winding I4might be longer in duration than the code impulses supplied to winding I5, because of the short-circuiting action of rectifier RI, whichrectifier provides a shunt path in its low resistance direction acrossthe highly inductive winding I5, through which path current from windingI5 tends to flow during the off period of the code, thereby delaying thedecay of the flux set up by winding I5 in the leakage path of the core.The decay of fiux in legs 8 and 9 being thus delayed, the primary fluxis caused to circulate longer through the main magnetic circuit of therelay to thereby prolong the length of the impulse of current induced inwinding I4. However, with resistor XI connected in series with rectifierRI and wind ing I5, and with rectifier R2 connected across the resistorin a manner such that the electromotive force of rectifier R2 opposesthe electromotive force of rectifier RI, as soon as the voltage fromrectifier R2 exceeds the potential drop across the resistor XI due tothe decaying current from winding I5, the current from the winding willbe stopped just as though it had been stopped by the opening of acontact of a relay, and as a result a sharp cut-off in the saturatingflux inthe leakage circuit of the relay is thereby effected. It,isreadily apparent, therefore, that the voltages of rectifiers R! and R2may be proportioned and designed so that as long as rectifier RI issupplied with current, the resultant of the voltages will cause theleakage magnetic circuit of relay DRIa to become saturated, but that,when rectifier RI becomes deeneregized, the voltage of rectifier R2 inopposing the decaying current of winding I5 prevents prolonged delay ofthe flux decay in the leakage magnetic circuit of the relay, wherebydistortion of the impulses induced in the secondary winding of the relayis prevented. The form of coded trackway energy supplied by relay DRIato rear subsection 3a-4 thus is improved and corresponds more closely tothe form of trackway energy supplied by the track transformer 'IT3 toadvance subsection 3-3a, whereby, as will be made clear presently,

the efficiency and operation of the decoding apparatus for the sectionis materially improved.

It should be noted that with relay DRIa constructed in the manner justdescribed, relatively little current will be supplied ,by rectifier R2to winding I5 during the off period of the code, since rectifier RI isarranged so that its high resistance direction is presented to the flowof current from rectifier R2.

Relay DRI located at signal location 4 of section 3-4 is substantiallysimilar in construction to relay DRIa just described, except that inrelay DRI a resistor X2 is connected across the output terminals ofrectifier RI. This resistor permits a small biasing flux to be built upin response to current supplied from rectifier R2 to winding I5 duringthe 01f period of the code, which flux is opposite in polarity to theflux set up in wind-- ing I5 in response to the resultant electromotiveforce of both rectifiers R! and R2. Thus, with relay DRI provided withresistor X2, a slight delay in flux growth in the leakage circuit ofrelay DRI will be effected when current is supplied from rectifier RI,since the biasing flux in legs 8 and 9 first must be neutralized beforethe saturating, fiux becomes effective to vary the inductive coupling ofthe primary and secondary windings of the relay. The impulse of currentinduced in secondary winding I4 of relay DRI accordingly will lag behindthe code impulse supplied to rec tifier RI. The parts of relay DRIpreferably are so proportioned that the lag of the induced irnpulse inwinding i4 substantially equals the in terval required for the decayingcurrent in winding I5 to drop to the potential of rectifier R2 after thecode impulse to rectifier RI is cut off. thereby causing the impulse ofcurrent induced in secondary winding I4 of relay DRI to havesubstantially the same length as the control code impulse supplied bythe track transformer 1T3 to the tracks rails of section 3 6.

Output Winding I4 of relay TR! is connected through the medium of arectifier R3 with a primary winding 28 of a decoding transformer DT4,and it is apparent, therefore, that winding I4 of relay DRI will supplytransformer DTd with impulses of unidirectional current which will havea code frequency and duration which corresponds to the frequency andduration of code present in the rails of section 3-4.

Decoding transformer DT4 is provided with a secondary winding ZIconnected through the medium of a rectifier R4 to a signal control relayH4 provided for section 3-4. The transformer DT4 is so proportioned anddesigned that relay H4 is energized and picked up whenever code of '75or 180 impulses per minute is induced in the secondary winding I4 ofrelay DRI, but that whenever steady or non-coded energy of the lower orgiven voltage is induced in secondary winding I4, relay H4 is released.Relay H4 consequently functions as a code detecting relay since it ispicked up whenever coded energy is supplied to relay DRI from the railsof the section, but is released whenever control Winding I5 of relay DRIis deenergized.

The decoding transformer BT 5 also supplies energy to another signalcontrol relay AJ i provided for section 3-4, which relay is connectedWith a portion of the primary winding 29 of transformer DT4 through adecoding unit DU'I8B. The details of construction of unit DE -E83 arenot shown in the drawings, but this unit usually comprises a rectifierand a reactor condenser tuning unit tuned to resonance at a frequencycorresponding to the 180 code whereby relay AJ4 is effectively energizedand is picked up when and only when. 180 code is supplied by the codefollowing relay DRl to the decoding transformer DT l. Relay Addtherefore functions as a code selecting relay since it is picked up when180 code is supplied to its associated code following relay but isreleased when '75 code is supplied to its associated code followingrelay from section B- i.

The code selecting relay AJ-t and the code detecting relay H l cooperateto selectively control the various aspects displayed by signal S4, inthe followir manner. When relays HE and AM are both pick-ed up, signal Sis caused to display its proceed indication over a circuit which may betraced from terminal B through front contact 222-t of relay E l, frontcontact 23 23a of relay A55, and the filament of lamp G of signal toterminal C. When the code detecting relay is picked up and the codeselecting relay [U5 is released, signal Sil then is caused to displaycaution indication over a circuit passing from terminal 13 through frontcontact 2Z--22a of relay H5, bacl: contact 2323b of relay A-l i, and thefilament of lamp Y of signal St to terminal C. When, however, bothrelays H4 and AM are eased, signal S t then is caused to display itindication over a circuit passng from ter el B through back contact 22--2b of relay and the filament of lamp R of ignal to terminal C.

The aboe selective control of signal S4 is effected relays H 3 and AM inthe following 35 manner: Section 3@ will be supplied with 180 or '75code according as the section next in advance is unoccupied or occupied.When section 3 is supplied with 180 code and the section is unoccupied,all parts of the apparatus will occupy the position in which they areshown in Fig. 1. Under the above conditions, relays HQ and AJ4 are bothpicked up, the circuit for lamp G of signal ileted whereby that signalis causeits procee indication, and 2 front contact Gfia of relay con tof coding device (3T is closed the section next in the rear of sectionS4 ed with 180 code also.

section is supplied with '75 code e section is unoccupied, relay H4 ispicked 'sy Add i released, is causing signal its caution indicationsince the completed. The rails of the section next rear of section 3-2,however, are still is occupied by a train, supplied to section ted awayirom the code followof that section. For example, occu the rearsubsection axles of the train then energy away from relay at winding !5of relay DRi henever a train occupies ion 3-3o, the train then energyfrom relay transnon-coded energy of the 70 g voltage is induced inwinding Id of relay 1155c and is supplied to the rear subsection Thissteady or non-coded energy is of such low voltage that it is ineffectiveto materially vary the reluctance of the leakage circuit of relay DR-l,and therefore the energy induced in output winding 14 under the lattercondition is substantially equivalent to the energy induced therein whenno energy is supplied from the track rails of the section to winding 15.It can be seen, therefore, that the coded trackway energy is shuntedfrom relay DRI whenever a train occupies either or both subsections3(1-4 or 3-3a, and that the two subsections when taken togethercooperate to provide a single tracksection which is responsive totraffic conditions in the same manner as if the rails of section 3--4where continuous conductors from one end of the section to the other.

When the coded trackway energy of a section is shunted away from itsassociated code following relay, the signal for that section then iscaused to display its restrictive or stop indication, since under theabove conditions the energy induced in winding M of the code followingrelay is non-coded energy of relatively low voltage. This non-coded lowvoltage energy supplied by relay DR to decoding transformer DT4 isineffective to cause energization of the signal control relays H4 andAJ4, so that both relays are released. Under the above conditions,signal S4 is controlled to its stop indication over back contact 2222bof relay H4, and the section next in the rear of the section 3-4 issupplied with '75 code over back contact fifib of relay H4. It isapparent, therefore, that the signal for a section is controlled to itsmost restrictive indica tion whenever its associated section isoccupied. It is also apparent that the section next in the rear ofsection 3-4 is supplied with trackway energy of 180 code at all timesexcept when section 3-4 is occupied, and that under the latter conditionthe rear section is then supplied with traclrway energy of '75 code. Thecode frequency or rate of the trackway energy supplied to each sectionis, therefore, governed by traffic condi tions in advance of thatsection,

From the foregoing, it is readily apparent that selective operation ofthe signal for a section is effected by traffic conditions in advance ofthat section, as determined by the particular form of trackway energysupplied to the rails of a section, which energy then is translated bythe decoding apparatus of a section to selectively con trol theassociated signal control relays. It can be seen that if distortedenergy having different characteristics than the originalcharacteristics of the trackway energy is supplied to the controlrelays, the relays then will be less efficient in distinguishing betweenthe several forms of trackway energy supplied to the track rails. Itfollows, therefore, that since relay DRla cascades trackway energy fromone subsection to the next with the minimum of distortion, and thatsince the energy reproduced in relay DR! has substantially the samecharacteristics as the trackway energy supplied to the section, theselective operation and efficiency of the signal control relays indistinguishing between the several forms of trackway energy ismaterially improved, and that the efficiency of the decoding apparatusas a whole is increased.

Referring now to Fig. 2, the apparatus in the form herein shown includesa code following relay DRZa of the saturation type located at thecut-section 3a of section 34, and also includes a similar relay DRZlocated at the signal location 4 of Fig. 2. The saturation relays shownin Fig. 2 are substantially similar in construction to the saturationrelays shown in Fig. 1, except that the biasing rectifier R2 and theresistor XI incorporated into the relays of Fig. l are now replaced bytwo coils Ilia and "5b mounted respectively on legs 8 and 9 of theleakage magnetic circuits of the relays of Fig. 2. The coils Ilia andI6!) of the relays of Fig. 2 are connected in series in such manner thatthe electromotive forces induced therein by the primary flux of therelays are additive, and the two coils are connected in series with theoutput winding M of the relays in such manner that the electromotiveforce induced in winding I4 is opposed by the electromotive. forces induced in the two windings "5a and llib, the parts of the relays being soproportioned and designed that during the interval the primary fluxdivides between its two magnetic circuits, the resultant of theelectromotive forces induced in coils Mia and IBD and in winding [4 issubstantially zero. With relays DB2 and DRZa constructed in theforegoing manner, it is apparent that the coils Mia and IBb areeffective to apply to the output winding M an electromotive force whichopposes the electromotive force present at times in the output windingof the relay, whereby, as will be made clear presently, distortion isprevented in the output of the relay.

The control winding l5 of each relay DB2 and DR2a is supplied withcurrent from its associated rectifier RI. Considering, for example,relay DRZa during the interval that its control winding l 5 isdeenergized, the primary flux of the relay at this time divided betweenthe main and the leakage magnetic circuits of the relay, to therebyinduce electromotive forces in winding l4 and in coils Mia and lSb. Aspointed out previously, the eelctromotive force induced in winding I4 isopposed and neutralized by the electromotive forces induced in the coilsMia and "5b, so that the resultant of the electromotive forces inducedat this time is substantially zero. At this time, therefore, no trackwayenergy is supplied from relay DRZa to the track rails of subsection311-4, and under the above conditions the relay functions as if thecircuit connection of secondary winding 14 of the relay and the railshad been opened by the opening of a contactof the usual tractivearmature type relay. In similar fashion, relay DB2 will supply no energyto the decoding transformer DT4 when control winding l5 of relay DRZ isdeenergized.

When, however, winding l5 of relay DRZa is supplied with current and asa result its leakage magnetic circuit is saturated, then theelectromotive force induced in winding I4 is greatly increased inmagnitude, while the magnitude of the electromotve forces induced incoils 5a and lBb drops and approaches a zero value. The resultant of theelectromotive forces at this time accordingly is relatively high and issubstantially equal to the electromotive force induced in winding l 4,so that under these conditions the rails of section 3a-4 are suppliedwith current of relatively high voltage. In like manner, when winding l5of relay DR2 is energized, the decoding transformer DT4 is supplied withan electromotive force of relatively large magnitude. The code output ofwinding M of relay DR2a or DR2, as the case may be, therefore is similarto the code supplied by the track transformer TT3 to the rails ofsection 34, in that energy is supplied from relay DRZa or DRZ onlyduring the "on period of the code and energy is not supplied during theoff period of the code, since there is substantially no residual outputof the relay, that is, no energy is induced in the relay during the operiod of the code.

It is readily apparent from the foregoing that, since control of theoutput of thecode following relay DRZ, which controls the signal for thesection, is effected by virtue of the difference in magnitude of theelectromotive forces supplied from the rails of the section to thecontrol winding l5 of the relay during the on and during the off periodof the code, if no electromotive force is present in the rails of thesection during the off period of the code, the magnitude of theelectromotive force induced in relay DRM and supplied by that relay tothe rails of the section can be much lower than if there is a residualoutput of the relay supplied to the rails of the section during the offperiod of the trackway code; Accordingly, it can be seen that operationof the code following relay of a section is effected by code impulses ofrelatively small magnitude.

Similarly, the operation of decoding transformer DT4 is based upon thedifferencein magnitude of the electromotive forces induced in winding Mof relay DRZ during the on and "off periods of the trackway codesupplied to the relay. It is apparent, therefore, that since there is noresidual output from relay DB2 so that transformer DT4 is not suppliedwith current during the off period of the code, no transfer of energy iseffected at that time and further, an induced impulse of relativelysmall magnitude will effectively operate the decoding transformer.

It should be noted that although relays DB2 and DRZ'a are particularlyeffective as code following relays, the relays may be used as ordinarycontrol relays with non-coded energy. In the event that the controlwinding P5 of the relay is supplied with non-coded energy, the relaywill have the same improved amplification that it possesses when codedenergy is supplied to the control winding. If used with non-codedenergy, during the-interval that the control winding of the relay isdeenergized the resultant of the electromotive forces induced in windingl4 and in coils lBa and I6?) is substantially zero, and the saturationrelay in this condition therefore corresponds to a relay of the tractivearmature type in its released condition, that is, with its front contactheld open. When, however, control winding I5 is energized by thenon-coded energy, the resultant of the induced electromotive forces thenbecomes relatively high so that the relay in this condition correspondsto a tractive armature type relay holding its front contact closed. Theconstruction and arrangement of the apparatus shown in Fig. 2 thereforeprovides a relay of the saturation type having substantially the samecharacteristics as a relay of the tractive armature type.

Referring now to Fig. 3, the relay DB3 (and in similar fashion relayDR3a) here shown, is provided with a magnetizable core 1 having fiveparallel legs 8, 9, II], II and I! connected together at each end toform an integral relay core structure. The main magnetic circuit ofrelay DRS, as here shown, comprises a common leg Hi and, in parallel,the core legs H and [1, upon which legs is mounted the secondary winding[4 of the relay, and which secondary winding comprises two coils Ma andNb disposed respectively on legs II and l! of core 1 and connected inseries in such manner that any electromotive forces induced therein areadditive. The leakage magnetic circuit of the relay comprises the commonleg l0 and, in parallel, the core legs 8 and 9, upon which legsis'mounted, respectively, the opposing coils Ifia and lBb connected inseries in such manner that any electromotive forces induced therein areadditive. The two coils I40. and 14b of output winding M are connectedin series with each other and with two coils lfia. and lfib disposed onthe leakage magnetic circuit of the relay in such manner that theelectromotive force induced in coils Ida and 14b oppo es theelectromotive force induced in coils 16a and H317, the parts preferablybeing so proportioned that the resultant of the electromotive forcesnormally induced in winding [4 and in coils lfia and 16b issubstantially zero. The control winding l5 of relay DB3 comprises, inaddition to the two coils Mia and i517 disposed on legs 8 and B of theleakage magnetic circuit, two other coils I50 and Mid disposedrespectively on legs H and H of the core, the other two coils I50 andlfid being connected in series with each other and in series with thefirst two coils l5a and i5!) so that the resultant electromotive forcenormally induced in winding i5 is substantially zero. The arrangement ofthe pairs of coils l5a and E51) disposed on the leakage magneticcircuit, and of the pairs I50 and Mid disposed on the main magneticcircuit, is such that when supplied with unidirectional current, eachpair of coils acts cumulatively to circulate a flux around the localmagnetic circuit formed by the two parallel core legs and the adjoiningtop and bottom portions of the core which form a portion of the magneticcircuit upon which that pair of coils is disposed.

Relay DB3 (and in like manner relay DRZU, also) further is provided witha biasing winding 18 which comprises a pair of coils 18a and H51)connected in series and disposed respectively on legs 8 and 9 of theleakage magnetic circuit, and another pair of coils 58c and I803connected in series and disposed respectively on legs H and I! of themain magnetic circuit, the two pairs of coils being connected in seriesacross the output terminals of a rectifier R5, which rectifier as shownhas its input terminals connected to terminal BX and a midtap of inputwinding E3 of relay DB3, but which rectifier may if so desired beenergized from a separate source of current. The coils forming one pairof coils in the biasing winding F8 are so arranged on one of themagnetic circuits of the relay that when supplied with unidirectionalcurrent, the flux created thereby aids the flux created by the pair ofcoils of the control winding 15 mounted on that circuit, whereas thecoils of the other pair of coils of the biasing winding iii are soarranged on the other magnetic circuit of the relay so that the fluxcreated thereby opposes the flux of the pair of coils of the controlwinding l5 mounted on the latter circuit. As shown, coils !8a and I81)are arranged on the leakage circuit so as to aid the flux created bycoils l5a and IE1) of control winding l5, and coils [8c and Mid are soarranged that when energized the fillX created thereby op poses the fluxcreated by coils I50 and l5d of control winding I5.

The operation of the saturation relay shown in Fig. 3 is as follows:Winding l3 of the relay is constantly energized by periodically varyingcurrent to set up a primary flux in the core 1 of the relay. Biasingwinding l8 also is constantly energized to set up a biasing flux in bothmagnetic circuits of the core. If, now, control winding [5 of the relayis deenergized, the primary fiux then divides between the two magneticcircuits of the core to thereby induce electromotive forces in outputwinding l4 and in coils lBa and 1622. As pointed out hereinbefore, theparts of the relay are so proportioned and arranged that when theprimary flux divides between the two magnetic circuits of the relay, theresultant of the electromotive forces induced in winding l4 and in coilsIda and 612 is substantially zero.

When, however, control winding I5 is energized to thereby set up a fluxin both magnetic circuits of the core, the flux set up by winding l5 inthe leakage circuit aids the biasing flux set up by its windings !8 inthat circuit, and at the same time the flux set up by winding 15 in themain circuit opposes the biasing flux set up in that circuit by windingIS. The parts of the relay are preferably so proportioned and designedthat with control winding 55 and biasing winding l8 both energized, theleakage magnetic circuit becomes magnetically saturated in response tothe fluxes created by windings l5 and i8, but in the main magneticcircuit, the biasing flux opposes and substantially neutralizes the fluxof winding it. Under the above conditions, therefore, substantially allthe primary flux is circulated through the main magnetic circuit of therelay and relatively little primary flux circulates through the leakagecircuit, so that a relatively high voltage is induced in secondarywinding l4 mounted on the main circuit and a relatively low voltage isinduced in coils Mia and IE2) mounted on that leakage circuit. Theresultant of the electromotive forces induced in winding H and in coilslSa and Nib at this time, therefore, is relatively large in magnitude.

From the foregoing, it is apparent that when control winding 15 of relayDB3 is deenergized,

the output of secondary winding 14 of the relay 1 is substantially zero,but that when control winding i5 is energized, the output of winding Mthen is at its maximum value. The arrangement and construction of relayDR-B therefore provides a saturation relay having characteristicssubstantially the same as a tractive armature type relay, in that underone condition of the relay no energy is permitted to flow in acontrolled circuit while under another condition of the relay energy ispermitted to flow in the circuit.

It should be noted that the above construction provides a saturationrelay which is controlled by supplying to its saturation winding arelatively small amount of energy. This reduced saturating energyeffects the control of the relay just described by virtue of the factthat a portion of the biasing winding aids the saturation winding toeffect the saturation of the leakage path of the relay, and theremainder of the biasing winding opposes the saturation winding to lowerthe reluctance of the main magnetic path of the relay, thereby causingthe primary flux to circulate through that circuit to thereby induce arelatively high electromotive force in the secondary winding of therelay. It is apparent, therefore, that since the saturation of theleakage circuit is effected by flux created in the control windingtogether with flux created in the biasing winding, the amount of currentsupplied to the control winding need be only that amount sufficient tosupply to the leakage path the differential in flux between thatnecessary to saturate the leakage path, and the flux already present inthe path due to the biasing winding. The amount of current supplied tothe control winding to control the output of the relay therefore ismaterially reduced by the provision of biasing windings on the relaycore.

The relays DB3 and DR3a, as shown in Fig. 3, may be employed as codefollowing relays to cascade trackway energy around the cut-section in atrack section, and to control the decoding apparatus for the coded trackcircuit, substantially in the same manner that was described in detailhereinbefore in connection with Figs. 1 and 2. It is believed that themanner in which the relays of Fig. 3 cooperate to improve the operationand eiiiciency of the decoding apparatus of the coded track circuit willbe readily apparent from an inspection of the drawings, together withthe foregoing description of the operation of the apparatus of Fig. 2,it being noted that the relays of Fig. 3 prevent distortion of the codedoutput of the relays substantially in the same manner that suchdistortion is prevented by the relays of Fig. 2. That is, the output ofthe relays of Fig. 3 during the off period of the code is substantiallyzero, so that the potential of the impulse induced in the relays of Fig.3 during the on period of the code need not be as great, whereby theoperation of the decoding transformer is eiiected by low peak potentialinduced in the relays of Fig. 3.

Although I have herein shown and described only three forms of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein. within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a code following relay of the saturation type, in combination, amagnetizable core provided with a primary winding normally supplied withalternating current, said core also carrying two other windings one ofwhich is a secondary winding inductively coupled with said primarywinding and the other of which is a saturation winding normally suppliedwith coded energy, said saturation winding being effective whenenergized to vary the inductive coupling of said primary and secondarywindings to cause the coded energy supplied to said saturation windingto be reproduced in said secondary winding, and means for preventingdistortion in the coded energy reproduced in said secondary winding inresponse to coded energy in said saturation winding, said means beingeffective to apply to one of said two other windings an electromotiveforce which opp ses the coded electromotive force present at times inthat winding.

2. In a code following relay of the saturation type, the combination of,a magnetizable core provided with a primary winding normally suppliedwith alternating current, said core also being provided with two otherwindings one of which is a secondary winding inductively coupled withsaid primary winding and the other of which is a saturation windingnormally supplied with coded energy, said saturation winding beingeiTective when energized to vary the inductive coupling of said primaryand said secondary wind ings to cause the coded energy supplied to saidsaturation winding to be reproduced in said secondary winding, and meansfor applying to one of said two other windings an electromotive forcewhich opposes the coded electromotive force pres-- ent at times in thatwinding, whereby distortion of the code output of said secondary windingis minimized.

3. In combination, a magnetizable core having two magnetic circuits oneof which comprises two parallel paths, a primary winding linking both ofsaid two magnetic circuits, two other windings one of which is asaturation winding comprising two coils one linking each of the twoparallel paths of said one magnetic circuit and connected in series insuch manner that the resultant electromotive force normally induced insaid saturation winding is substantially zero, the other of said twoother windings being a secondary winding disposed on the other of saidtwo magnetic circuits for inductive relationship with said primarywinding, means for supplying periodically varying current to saidprimary winding for setting up a flux in each of said two magneticcircuits, means for at times supplying coded unidirectional current tosaid saturation winding for varying the reluctance of said one magneticcircuit whereby the flux in said other magnetic circuit is varied instep with the coded current supplied to said saturation winding, andmeans for applying to one of said two other windings an electromotiveforce which opposes the electromotive force present at times in thatwinding whereby distortion is prevented in the coded current induced insaid secondary winding in response to the coded current supplied to saidsaturation winding.

4. In combination, a magnetizable core provided with a primary windingwhich is constantly supplied with periodically varying current, asecondary winding on said core inductively coupled with said primarywinding, a saturation winding on said core effective when energized tovary the inductive coupling of said primary and secondary windings, asource of coded alternating current, means including a rectifier forsupplying to said saturation winding impulses of rectified current fromsaid source of coded alternating current, and means for applying to saidsaturation winding an electromotive force which opposes theelectromotive force due to said rectifier to counteract the shuntingaction of said rectifier whereby distortion is prevented in the codedenergy induced in said secondary winding in response to the impulses ofrectified current supplied to said saturation winding.

5. In combination, a magnetizable core provided with a primary windingwhich is constantly supplied with periodically varying current, asecondary winding on said core inductively coupled with said primaryWinding, a saturation winding on said core eiiective when energized tovary the inductive coupling of said primary and secondary windings, aresistor, a source of coded alternating current, means including arectifier connected in series with said resistor for supplying to saidsaturation winding impulses of rectified current from said source ofcoded alternating current, and means for impressing across said resistora voltage which opposes that due to said rectifier to provide a sharpcut-off in the current induced in said secondary winding by the currentflowing in said primary winding in response to the impulses of rectifiedcurrent supplied to said saturation winding.

6. In combination, a magnetizable core having two magnetic circuits oneof which comprises two parallel paths, a primary winding linking both ofsaid two magnetic circuits, a secondary winding comprising three coilsone disposed on each of said two parallel paths of said one magneticcircuit and the third disposed on the other magnetic circuit, said coilsbeing connected in series in such manner that the resultantelectromotive force normally induced in said output winding when saidprimary winding is supplied with alternating current is substantiallyzero, a saturation winding comprising two coils one disposed on each ofsaid two parallel paths of said one magnetic circuit and connected inseries in such manner that when supplied with unidirectional current thecoils act cumulatively to circulate a flux through said two parallelpaths of said one magnetic circuit, means for supplying alternatingcurrent to said primary winding, and means for at times supplyingunidirectional current to said saturation winding, whereby thereluctance of said one magn tic circuit is at times varied to vary theresultant electromotive force induced in said secondary winding,

'7. A relay of the saturation type comprising, in combination, amagnetizable core having two magnetic circuits, a primary windinglinking both said circuits and normally supplied with alternatingcurrent for setting up a primary flux in said core, a biasing windinghaving a portion disposed on each circuit, said biasing winding normallybeing supplied with unidirectional current for establishing a givencondition of reluctance in each circuit, a secondary winding having aportion disposed on each circuit, said portions being connected inseries in such manner that the resultant of the electromotive forcesinduced in said secondary winding under the given condition ofreluctance of said circuits is substantially zero, a saturation windinghaving a portion disposed on each circuit one portion of which iseffective when supplied with unidirectional current to increase thereluctance of one circuit and the other portion of which is effectivewhen supplied with said unidirectional current to decrease thereluctance of the other circuit, and means for at times supplyingunidirectional current to said saturation winding whereby the resultantof the electromotive forces induced in said secondary winding by saidprimary flux is relatively large in magnitude.

8. A relay of the saturation type comprising, in combination, amagnetizable core having two magnetic circuits, a primary windinglinking both said circuits and normally supplied with alternatingcurrent for setting up a primary flux in said core, a biasing windinghaving a portion disposed on each circuit, said biasing winding normallybeing supplied with unidirectional current for establishing a givencondition of reluctance in each circuit, a secondary winding having aportion disposed on each circuit, said portions being connected inseries in such manner that the resultant of the electromotive forcesinduced in said secondary winding under the given condition ofreluctance of said circuits is substantially zero, a saturation windinghaving a portion disposed on each circuit in such manner that when saidsaturation winding is supplied with unidirectional current the resultantof the electromotive forces induced in said secondary winding becomesrelatively large in magnitude, and means for at times supplying saidsaturation winding with unidirectional current.

9. A relay of the saturation type comprising, in combination, amagnetizable core having two magnetic circuits each having two parallelpaths, a 1: mary winding linking both of said magnetic circuits, saidprimary winding normally being supplied with periodically varyingcurrent for setting up a primary flux in each or said magnetic circuits,a secondary winding comprising four coils one disposed on each of theparallel of said two magnetic circuits, said four coils being connectedin series in such manner that the electromotive forces normally inducedin the pair of coils disposed on each of said magnetic circuits areadditive and the resultant of the electromotive forces normally inducedin both pairs of coils when said primary flux circulates through bothsaid magnetic circuits is substantially zero, biasing winding comprisingfour coils one disposed on each of the parallel paths of said twomagnetic circuits, said four coils of the biasing winding beingconnected in series in such manner that the resultant of theelectromotive forces normally induced in the pair of coils disposed oneach of said magnetic circuits is substantially zero, said biasingwinding normally being supplied with unidirectional current for settingup a biasing flux in each of said two magnetic circuits whereby theprimary flux normally is circulated through both said two magneticcircuits, a saturation winding comprising four coils one disposed oneach of the parallel paths of said two magnetic circuits, said fourcoils of the saturation winding being connected in series in such mannerthat the resultant of the electromctive forces normally induced in thepair of coils disposed on each magnetic circuit is substantially zero,one pair of coils of the saturation winding being arranged on onemagnetic circuit in such manner that when supplied with unidirectionalcurrent the flux created thereby aids the flux supplied to that circuitby said biasing winding whereby the reluctance of that circuit isincreased, the other pair of coils of the saturation winding beingarranged on the other magnetic circuit in such manner that when suppliedwith said unidirectional current the flux created thereby opposes theflux supplied to said other circuit by said biasing winding whereby thereluctance of said other circuit is decreased and substantially all theprimary flux circulates through said other path and the resultant of theelectromotive forces induced in said secondary winding becomesrelatively high in magnitude, and means for at times supplyingunidirectional current to said saturation winding.

10. In combination, a five-legged magnetizable core having two magneticcircuits both including in common a central leg of said core, each saidcircuit also including two other legs of said core in parallel, aprimary winding disposed on said common central leg of said core andconstantly supplied with periodically varying current for setting up aprimary flux in each of said two magnetic circuits, a secondary windingcomprising two pairs of coils one pair of which is disposed one coil oneach of the two parallel legs of one of said magnetic circuits and theother pair of which is disposed one coil on each of the two parall llegs of the other of said magnetic circuits, the coils of each pairbeing connected in series in such manner that the electromotive forcesinduced therein are additive and said pairs of coils being connected inseries in such manner that the resultant electromotive force normallyinduced in said secondary winding is substantially zero, a biasingwinding constantly supplied with unidirectional current and comprisingtwo pairs of coils one pair of which is disposed one coil on each of thetwo parallel legs of said one magnetic circuit and the other pair ofwhich is disposed one coil on each of the two parallel legs of saidother magnetic circuit, said coils of the biasing winding beingconnected in series in such mannor that when supplied withunidirectional current the coils of each pair act cumulatively tocirculate a biasing flux through a local magnetic circuit comprising thetwo parallel legs of the associated magnetic circuit of the core uponwhich that pair of coils is disposed, a saturation winding comprisingtwo pairs of coils one pair of which is disposed one coil on each of thetwo parallel legs of said one magnetic circuit and the other pair ofwhich is disposed one coil on each of the two parallel legs of saidother magnetic circuit, said coils of said saturation winding beingconnected in series in such manner that when supplied withunidirectional current the coils of one pair of coils act cumulativelyto circulate a saturating flux through the local magnetic circuit of theassociated magnetic circuit of the core in agreement with the biasingflux of that local circuit, whereby that local magnetic circuit issubstantially magnetically saturated, and the coils of the other pair ofcoils of the saturation winding act cumulatively to circulate asaturating flux through the local magnetic circuit of the associatedmagnetic circuit of the core in opposition to the biasing flux of thatlocal circuit, whereby the biasing and saturating fluxes of the lastmentioned local circuit substantially cancel each other, and means forat times supplying unidirectional current to said saturation winding tothereby vary the resultant electromotive force induced in said secondarywinding of said relay.

11. In combination, a section of railway track, means for supplyingcoded alternating trackway energ to the rails of said section, a relaytransformer having its primary receiving energy from the rails of saidsection, a track rela of the saturation type comprising a magnetizablecore provided with a primary winding constantly connected with a sourceof alternating current, said relay having two other windings disposed onsaid core one winding of which is a secondary winding inductivelycoupled with said primary windin and the other winding of which is asaturation winding receiving energy from the secondary of said relaytransformer, said saturation winding being eifective when energized tovary the inductive coupling of said primar and secondary windings ofsaid relay to cause the coded energy supplied to the saturation windingto be reproduced in said secondar winding, said relay also having meansto apply to one of said two other windings an electromotive force whichopposes the electromotive force present at times in that winding tothereby prevent distortion in the coded output of said track relay, anda signal for governing trafiic in said section controlled by the codedoutput of said track relay.

12. In combination, a section of railway track, means for supplyingcoded trackway energy to the rails of said section, a track relay of thesaturation type comprising a magnetizable core provided with a primarywinding constantly supplied with alternating current, said relay havingtwo other windings disposed on said core one winding of which is asecondary winding inductively coupled with said primary winding and theother winding of which is a saturation winding effective when energizedto vary the inductive coupling of said primary and secondary windings,means for supplying unidirectional current from the rails of saidsection to said saturation winding to cause said relay to reproduce insaid secondary winding the coded trackway energy supplied to the railsof said section, said relay also having means to apply to one of saidtwo other windings of the relay an electromotive force which opposes theelectromotive force present at times in that winding whereby distortionis prevented in the coded energy reproduced in the secondy winding ofsaid relay, and

a signal governing trafiic in said section controlled by the codedenergyreproduced in the secondary winding of said relay.

13. Decodingapparatus for coded track circuits comprising a track relayof the saturation typehaving a magnetizable core provided with a primarywinding which is constantly supplied with periodically varying currentfor setting up a flux in said core, two other windings on said core oneof which is a secondary winding induc- I tromotive force which opposesthe electromotive force present at times in that winding to therebyprevent distortion of the coded current induced in said secondarywinding in response to the coded energy supplied said saturationwinding,

a decoding transformer supplied with current from said secondarywinding, and signal control means receiving energy from saidtransformer.

14. In combination, a section of railway track, means for supplyingcoded alternating trackway energy of a given'code rate to the rails ofsaid section, a relay transformer having its primary winding receivingenergy from the rails of said section, a code following relay of thesaturation type having a primary winding constantly supplied withcurrent from a source of alternating 1 current, said relay having asecondary winding inductively coupled with said primary winding, saidrelay also having a saturation winding effective when energized forvarying the inductive coupling of said primary and secondary windings, aresistor, circuit means including a rectifier connected in series withsaid resistor for supplying impulses of rectified current to saidsaturation winding from said relay transformer whereby when codedcurrent is supplied to the track rails there will be induced in thesecondary winding of said relay pulses of alternating current having arate corresponding to the code rate, means for impressing across saidresistor a biasing voltage which opposes the voltage of said rectifierto provide a sharp cut-off in the current induced in said secondarywinding, and traflic controlling apparatus controlled by the alternatingcurrent which is induced in said secondary winding in step with theimpulses of rectified current supplied to said saturation winding.

15. In combination with a section of railway track having means forsupplying to the track rails of said section trackway energy coded at afirst rate under certain conditions and at a second rate under otherconditions, a code following relay of the saturation type comprising amagnetizable core having a primary winding constantly supplied withalternating current and a secondary winding inductively coupled withsaid primary winding, said relay also having a saturation windingdisposed on said core effective when supplied with unidirectionalcurrent to vary the inductive coupling of said primary and secondarywindings, means for supplying unidirectional current to said saturationwinding from the track rails of said section whereby pulses of energyare reproduced in the secondary winding of the relay having a rate whichcorresponds to means for applying to said saturation winding anelectromotive force which opposes the electromotive force supplied tothat winding from the track rails of the section to cause a sharpcut-off in the coded energy reproduced in the secondary winding of therelay, and a signal governing traific in said section and selectivelycontrolled by the energy reproduced in said relay in accordance with therate at which such energy is coded.

16. In combination with a section of railway track having means forsupplying to the rails of the section alternating trackway energy codedat a first rate under certain conditions and at a second rate underother conditions, a code following relay of the saturation typecomprising a inagnetizable core having a primary winding constantlyconnected with alternating current and a secondary winding inductivelycoupled with said primary winding, said relay also having mounted onsaid core a saturation winding effective when supplied withunidirectional current to vary the inductive coupling of said primaryand secondary windings, means including a rectifier for supplyingunidirectional current from the track rails to said saturation windingwhereby energy is reproduced in the secondary winding of the relay codedin accordance with the rate at which the trackway energy then is coded,means for supplying to said saturation winding an electromotive forcewhich opposes the electromotive force of said rectifier whereby theshunting action of said rectifier is minimized to cause a sharp cut-onin the coded energy reproduced in the secondary winding of the relay,and a signal governing traffic in said section and selectivelycontrolled by the energy reproduced in said relay in accordance with therate at which such energy is coded.

1'7. In combination with a section of railway track having means forsupplying to the rails of the section alternating trackway energy codedat a first rate under certain conditions and at a second rate underother conditions, a track relay of the saturation type comprising amagnetizable core having a primary winding constantly connected withalternating current and a secondary winding inductively coupled withsaid primary winding, said relay also having mounted on said core asaturation winding effective when sup-plied with unidirectional currentto vary the inductive coupling of said primary and secondary windings, aresistor, a first rectifier receiving energy from the track rails ofsaid section, said saturation winding being connected in series withsaid resistor across the output terminals of said first rectifierwhereby unidirectional current is supplied to said saturation winding tocause the energy induced in the secondary winding of the relay to becoded in accordance with the rate at which the trackway energy is coded,a second rectifier connected across said resistor and arranged in suchmanner that its electromotive iorce opposes the electromotive force ofsaid,

first rectifier whereby the shunting action of said first rectifier isminimized to cause a sharp cut-off in the coded energy reproduced in thesecondary winding of the relay, and a signal governing trafiic in saidsection and selectively controlled by the energy reproduced in saidrelay in accordance with the rate at which such energy is coded.

18. In combination with a stretch of railway track having means forsupplying coded trackthe rate at which the trackway energy is coded,

way energy to the rails of the section, a code following relay, saidrelay having a five-legged magnetizable core provided with two magneticcircuits having a central leg of the core in common and each circuithaving two other legs of the core in parallel, said relay having aprimary winding disposed on said central leg and constantly suppliedwtih alternating current for setting up a primary fiux in both saidmagnetic circuits, said relay having a biasing winding constantlysupplied with unidirectional current and comprising two pairs of coilsone pair disposed one coil on each of the two parallel legs of one ofsaid magnetic circuits and the other pair disposed one coil on each ofthe two parallel legs of said other magnetic circuit, said coils of saidbiasing winding being connected in series in such manner that the coilsof each pair of coils act cumulatively to circulate a biasing fluxthrough the two parallel legs of the associated magnetic circuit, saidrelay also having a secondary winding comprising two pairs of coils onepair of which is disposed one coil on each of the two parallel paths ofsaid one magnetic circuit and the other pair being disposed one coil oneach of the two parallel paths of said other magnetic circuit, saidcoils of said secondary winding being connected in series in such mannerthat the voltages induced in each coil of a pair are additive and theresultant of the voltages normally induced in both pairs of coils issubstantially zero, said relay having a saturation winding receivingenergy from the rails of said section and comprising two pairs of coilsone pair of which is disposed one coil on each of the two parallel legsof said one magnetic circuit and the other pair is disposed one coil oneach of the two parallel legs of said other magnetic circuit and saidcoils of said saturation winding being connected in series in suchmanner that one pair of coils acts cumulatively to circulate asaturating flux through its two associated parallel legs of the core inagreement with the biasing flux and the other pair of coils actscumulatively to circulate a saturating flux through its two associatedparallel legs of the core in opposition to said biasing flux, wherebythe reluctances of said two magnetic circuits of said core are varied insuch manner that impulses of relatively large resultant electromotiveforce are induced in said secondary winding of the relay having a ratecorresponding to the rate of the coded energy supplied to the rails ofthe section, and a signal for governing trafiic in said sectioncontrolled by the impulses of relatively large electromotive forceinduced in said secondary winding of the relay.

19. In combination with a section of railway track divided intoadjoining advance and rear subsections, means for supplying codedtrackway energy to the rails of said advance subsection, a codefollowing relay of the saturation type having a magnetizable coreprovided with a primary winding constantly supplied with alternatingcurrent, said relay having two other windings disposed on said core oneof which is a secondary winding inductively coupled with said primarywinding and the other of which is a satiu'ation winding efiective whensupplied with current for varying the inductive coupling of said primaryand secondary windings of the relay, means for connecting said secondarywinding across the track rails of said rear subsection, means forsupplying current from the track rails of said advance subsection tosaid saturation winding whereby impulses of relatively largeelectromotive force having a rate which corresponds to the rate of thetrackway energy supplied to the rails of said advance subsection arecaused to be induced in said secondary winding and are supplied to thetrack rails of said rear subsection, and means for applying to one ofsaid two other windings of said relay an electromotive force whichopposes the electromotive force present at times in that winding tothereby prevent distortion in the impulses of trackway energy suppliedto the rails of said rear subsection.

20. In combination with a section of railway track divided intoadjoining advance and rear subsections, means for supplying codedalternating trackway energy to the rails of said ad- Vance subsection, acode following relay of the saturation type having a magnetizable coreprovided with a primary winding constantly supplied with alternatingcurrent, said relay having a secondary winding disposed on said core ininductive relationship with said primary Winding, said secondary Windingbeing connected across the track rails of said rear subsection, saidrelay having a saturation winding disposed on said core and. efiectivewhen supplied with unidirectional current to vary the inductive coupling of said primary and secondary windings of the relay, meansincluding a rectifier for supplying unidirectional current from therails of said advance subsection to said saturation winding to causeimpulses of current of relatively high magnitude having a rate whichcorresponds to the rate of the trackway energy supplied to said advancesubsection to be induced in said secondary winding of the relay and tobe supplied to the rails of said rear subsection, and means for applyingto said saturation winding an electromotive force which opposes theelectromotive force due to said rectifier whereby the shunting action ofsaid rectifier is minimized to prevent distortion in the impulses oftrackway energy supplied to said rear subsection.

21. A relay of the saturation type comprising two magnetic paths bothhaving a common portion linked by an input Winding normally suppliedwith alternating current, an output winding comprising two portions onedisposed on each of said two magnetic paths and connected in series andproportioned in such manner that the voltages induced therein inresponse to the primary fiux set up in said paths by said input windingoppose and substantially cancel each other, another winding linking atleast one of said two paths, and means for at times supplying to saidother winding unidirectional current for varying the relativereluctances of said two paths whereby to shunt the primary flux createdby said input winding away from said one path and cause a resultantvoltage of relatively large magnitude to be induced in said outputWinding.

22, A relay of the saturation type characterized by the fact that theoutput thereof varies between a predetermined maximum value and asubstantially zero minimum value, comprising the combination with amagnetizable core having two magnetic circuits provided with a commonprimary winding normally supplied with alternating current for settingup a primary fiux in both of said two circuits, of two windings a firstof which has two portions one disposed on each of said two circuits andthe second winding of which is disposed on at least a particular one ofsaid two circuits, means for supplying unidirectional current to saidfirst winding for establishing a given condition of relative reluctancein said two circuits, other means for supplying unidirectional currentto said second winding of a polarity such that said particular onecircuit is supplied with flux which opposes the flux supplied thereto bysaid first winding whereby the relative reluctances of said two circuitsis modified and the primary flux is shunted away from, the other of saidtwo circuits, an output winding disposed on at least one of saidmagnetic circuits, and means for controlling the supply ofunidirectional current to at least one of said two windings whereby tocontrol the magnitude of electromotive force induced in said outputwinding in accordance with the supply of current to said one winding.

23. A relay of the saturation type characterized by the fact that theoutput thereof varies between a predetermined maximum, value and asubstantially zero minimum value, comprising the combination with amagnetizable core having two magnetic circuits both including a commonportion linked by a common primary winding normally supplied withalternating current for setting up a primary flux in both of said twocircuits, of a first winding having two portions one disposed on each ofsaid two circuits, means for supplying unidirectional current to saidfirst winding for setting up a given condition of relative reluctancesin said two circuits, other means including a second winding disposed ona particular one of said circuits and supplied with unidirectionalcurrent for supplying said one circuit with flux which opposes the fluxset up by said first winding whereby the relative condition ofreluctances is modified and the primary fiux is shunted away from theother of said magnetic circuits, and an output winding disposed on atleast one of said magnetic circuits for inductively receivingelectromotive forces from said primary winding under the control of thesupply of energy to said first winding.

24. In combination, a five-legged magnetizable core having two magneticcircuits both including in common a central leg of said core and each ofsaid circuits also including two other legs of said core in parallel, aprimary winding disposed on said common central leg of said core andconstantly supplied with periodically varying current for setting up aprimary flux in both of said two circuits, two windings a first of whichcomprises two pairs of coils one pair for each of said two circuits andeach pair disposed one coil on each of the two parallel legs of itsassociated circuit and the second winding of which comprises at leastone pair of coils disposed one coil on each of the two parallel legs ofa particular one of said circuits, the two coils comprising each pair ofcoils of said two windings being arranged on the two parallel legs ofits associated circuit in such manner that when supplied withunidirectional current both coils cooperate in circulating a fiuxthrough a closed magnetic circuit including in series the two parallellegs of its associated circuit, means for supplying unidirectionalcurrent to said first winding for establishing a given condition ofrelative reluctance in said two circuits, other means for supplyingunidirectional trolling the supply of unidirectional current to at leastone of said two windings whereby to control the magnitude of theresultant electromotive force induced in said output winding inaccordance with the supply of current to said one winding.

BERNARD E. OHAGAN.

